Laser additive manufacturing of multimaterials with hierarchical interlocking interface via a flexible scraper-based method

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Superalloy/copper structures are promising for application in rocket combustion chambers and can integrate the high strength of superalloys and the high thermal conductivity of copper in a single component to improve performance and work efficiency. The natural hierarchical interlocking structure can provide inspiration for the interface design of metallic multimaterial structures to resolve or minimise the critical issue of interfacial bonding reliability arising from the distinct physical properties of materials (thermal expansivity, thermal conductivity, etc.). In this study, IN718/CuCrZr multimaterial structures with hierarchical interlocking interfaces were designed and manufactured using laser powder bed fusion (LPBF) via a flexible scraper-based method. The evolution of microstructure at the interface and mechanical properties were investigated. The thermomechanical behaviour during the LPBF process, interfacial bonding mechanisms, and deformation mechanisms are discussed. Compared to printing CuCrZr before IN718, printing IN718 before CuCrZr is a promising printing sequence for reducing the stress concentration and lack-of-fusion defects, and promoting material intermixing at the interface. A hierarchical interlocking interface design can promote material intermixing and grain refinement at the interface. In addition, the hierarchical interlocking interface design can improve the stress distribution and deflect the fracture path at the interface, which helps increase energy dissipation and enhance interfacial bonding. Three-point flexural test results show that the ultimate flexural strength of the N1 samples was increased by 15% compared to the N0 samples. This study demonstrates the feasibility of changing the interfacial stress distribution and deformation behaviour of LPBF-processed metallic multimaterial parts through a hierarchical interlocking interface design, which may provide new ideas and methods for the development of multimaterial parts with high interfacial bonding strength and reliability.